1. Technical Field
The present invention relates to internal combustion engine ignition systems. More particularly, it relates to a method of balancing air to fuel ratios of individual cylinders in an automobile's engine.
2. Discussion
The prior art includes a variety of conventional methods for detecting and using ionization current in a combustion chamber of an internal combustion engine. However, each of the various conventional systems suffers from a great variety of deficiencies. For example, prior art ionization current detection circuits are generally too slow and generate a current signal with low signal-to-noise ratio.
Typically, the primary coil of an ignition system is charged close to a desired amount of energy as a function of engine operational conditions such as the local mixture air to fuel ratio, pressure, temperature, and engine gas recirculation concentration. Since the breakdown voltage and spark duration at the discharge moment can be different from cycle to cycle, it is desirable to monitor some of these parameters. Section A discloses how these parameters are monitored.
It is desirable to run an automobile internal combustion engine at its minimum timing for best torque spark timing, if possible, for improved fuel economy. Due to the lack of a combustion feedback control system in the prior art, the ignition timing is controlled in open loop based upon an minimum timing for best torque timing table based upon the engine mapping data. The disadvantage of this approach is that it requires a long calibration process and the minimum timing for best torque timing control system is sensitive to changes in system parameters.